The invention relates to the field of hard disk cooling. In particular, the invention relates to a cooling system utilizing fanning structure driven by the spindle motor.
Magnetic recording disks (MRD""s) are continuously improved to provide higher storage capacity, data transfer rates, and lower access times. The increase of the rotational speed of the hard disk(s) is one approach to improve the performance of the MRD""s. Additionally, electronics that are more powerful are packaged inside the housing of the MRD to perform the necessary operational tasks related to the reading and writing of data on the hard disk(s).
The overall dimensions of MRD""s are defined by a number of standardized classes. These standardized dimensions of the MRD housings force the development of increasingly compact designs. To meet the increasing performance demands, MRD""s are manufactured with smaller functional features and higher precision. Especially the flying height of the slider over the surface of the hard disk is being continuously reduced. As a result, the internal area of MRD""s becomes more sensitive to humidity and particularly to dust. To keep dust away, MRD housings are therefore typically sealed. Only a relatively small opening remains to adjust the internal air pressure to variations of the surrounding atmosphere without appreciable air exchange.
The performance increase of MRD""s results in an increase of internally generated thermal energy. Sources of the thermal energy are the electronics, the spindle motor, the voice coil, the friction of the disk driven air and friction of the slider on the hard disk surface. With the surface area of the housing remaining constant, the increased thermal energy can only be dissipated by maintaining a higher temperature difference between the housing surface and the surrounding environment. Hence, for a given temperature of the surrounding environment, the housing temperature and consequently the internal temperature of the MRD are higher. Internal temperature rise of the MRD becomes an increasingly dominant limitation for the optimization of MRD""s. In addition, it is desirable to keep the internal temperature as constant as possible to maintain thermally induced deformations of the high precision features of the disk within the ever tighter tolerances.
With smaller flying heights of the sliders over the disk surfaces, the air viscosity also becomes a more and more significant consideration. The slider""s air bearing surfaces are designed to provide a constant flying height for a given air viscosity. Hence, changes in the air viscosity due to temperature differences result in changes of the flying heights. These flying height variations have to remain at a minimum. High thermal energy can destabilize the magnetic orientation of the bit wise stored data on the media. The thermal energy is usually represented by k times T where k is the Boltzman constant and T is the absolute temperature. This unfavorable destabilization occurs when the volume of the magnetic particles representing the bit decreases in disk designs with high data densities. An ability to reduce the thermal energy will enhance the magnetic stability of the bit wise stored data.
To limit the internal temperature rise a number of inventions are disclosed in the prior art. These inventions mainly improve the heat convection of the MRD housing by introducing and directing an air flow along a part or along the whole housing. For instance, U.S. Pat. Nos. 5,912,799, 5,886,639, 5,793,608, 5,796,580, and 5,673,029 describe such inventions. In all these inventions, the cooling is provided by a device, which is independent from the MRD. This type of cooling therefore cannot take into account specific cooling requirements that vary between individual MRD""s. MRD manufacturers are not able to take such cooling systems into account in computing the maximum operational thermal energy output, since there does not exist a common standard among computer manufacturers for heat drain provided within the computer chassis.
To eliminate the limitations described in the paragraph above, U.S. Pat. No. 5,870,247 introduces a fan system integrated in a hard disk drive. Adjacent to the hard disk drive is attached an air channel structure including a miniaturized fan. The fan draws air from the surroundings and blows it through the channel structure. The channel structure is designed to draw thermal energy from the essentially sealed operational volume of the hard disk drive and to drain that thermal energy into the fan induced air stream. The structural combination of hard disk drive and fan cooling system allows to increase MRD performance parameters and raise the operational thermal energy. Unfortunately, this is accomplished at the expense of available operational volume of the hard disk drive.
General limitations of fan cooling systems are, for instance:
their propensity to accumulate dust deposits, which significantly reduces the convective properties of the cooling surfaces;
their efficiency dependence on the surrounding air temperature;
their voluminous space requirements; and
their noisiness.
Therefore, there exists a need for a MRD cooling system that can be structurally integrated within the MRD housing without reducing the available operational volume; that is insensitive to dust, highly independent of the surrounding air temperature, and preferably noiseless. The present invention introduces such a system.
It is a primary object of the present invention to provide an MRD cooling system that can be structurally integrated within the MRD housing without reducing the available operational volume.
It is another object of the present invention to provide an MRD cooling system that is insensitive to dust.
It is a further object of the present invention to provide an MRD cooling system that is highly independent of the surrounding air temperature and air condition like, for instance, humidity and air velocity.
Finally, it is an object of the present invention to provide a MRD cooling system that is essentially noiseless.
The present invention utilizes a rotating fanning structure driven by the spindle motor to generate cooling air streams in a cooling system for a magnetic recording disk (MRD).
In the preferred embodiment of the invention, the rotating fanning structure is combined with the hard disk structure. The fanning structure induces a cooling air stream on the essentially closed air volume inside the MRD housing. The cooling air stream is directed towards a thermal bridging element that reaches through the MRD housing. The thermal bridging element drains the thermal energy received from the cooling air stream into the surrounding environment. The thermal bridging element has internal and external access areas. The internal access area corresponds in its shape and location to the internal cooling air stream. The external access area may be an air contact area to drain the thermal energy into the surrounding air. The external access area may also be a structural contact area to drain the thermal energy into a frame structure or other thermally conductive structures of the MRD mounting site.
The internal fanning structure is incorporated into the hard disk and operates according to the principles of a radial fan and/or an axial fan.
In an alternate embodiment, the rotating fanning structure operates outside the self-contained operational MRD volume. The external fanning structure utilizes air from the surrounding environment to create a cooling air stream along the thermal bridging element. The thermal bridging element is of a form and placed at a location that correspond to the internal thermal path of the MRD. Form and location of the thermal bridging element eventually correspond also to an external cooling air stream generated by an external rotating fanning structure. The eventual external fanning structure has a form that corresponds to the known working principles of a radial fan and/or an axial fan. The external fanning structure may be combined with the internal fanning structure.
The thermal bridging element may be a Peltier-element, which provides a controllable thermal bridge. The Peltier-element allows, on the one hand, to adjust the thermal drain from the MRD interior and thereby helps to reduce the operational temperature bandwidth inside the MRD. On the other hand, the Peltier-element allows to drain more thermal energy for a given temperature difference between the thermal bridging element and the surrounding environment. Consequently, the maximal temperature inside the MRD can be kept at a lower level and internal temperature variations remain low.